Pesticide efficacy trial on pecan aphid control

PECAN:

In 2013, Drs. Mark A. Muegge and Salvador Vitanza evaluated the efficacy of several insecticides for black-margined aphid (BMA) control.  This study was conducted in a commercial pecan orchard near Fabens, TX.  A single pecan tree constituted an experimental unit.  Each experimental unit was bordered by untreated pecan trees as buffers to help reduce potential drift contamination.  Experimental units were arranged in a randomized complete block design with 10 treatments replicated 4 times.  Insecticide applications were made using a high pressure sprayer calibrated to deliver 100 gallons per acre (gpa) at 100 pounds per square inch (psi).  From each experimental unit 3 randomly selected compound leaves were examined for BMA.  Adult and nymph aphids found were counted separately and recorded.  Treatments were applied on 11 Oct after pre-treatment samples had been collected.  Post treatment samples were taken at 10 and 25 days after treatment.  All data were subjected to analysis of variance (ANOVA).  Treatment mean separation was performed using Fisher's Protected LSD (P=0.05). 

Although total BMA densities were moderately high they never exceeded economically damaging population densities throughout the duration of this test.  Prior to treatment application, BMA adult and nymph population densities were statistically equal among untreated check and treated plots.  At 10DAT the Induce, Agriflex, Agrimek and Admire Pro treatments did not significantly reduce BMA adult population density.   All treatments except Agriflex and Admire Pro significantly reduced BMA nymph population densities.  At 25DAT only the Beleaf treated trees had significantly lower BMA adult population densities relative to the untreated check trees and BMA nymph populations were not significantly lower in any of the treated trees relative to the untreated check.  However, population densities of BMA nymphs were substantially lower in the Endigo, Voliam and Beleaf treated trees relative to the untreated check trees.  Interestingly, the NIS and Agriflex treated trees had significantly higher BMA nymph population densities relative to the untreated check trees.   Whether this result is a real cause and effect or a result of experimental and or sampling error requires further studies. 

		Mean BMA adults/3 Compound Leaves			Mean BMA nymphs/3 Compound Leaves
Treatment	Rate (oz/acre)	0 DAT	10 DAT	25 DAT	0 DAT	10 DAT	25 DAT
UTC	-	8.2	7.8ab	4.2bc	14.3	24.2a	11.3bcd
Induce	4.8	6.9	7.9a	9.2a	10.7	11.8bc	31.7a
Agriflex+NIS	5.5	4.6	5.7abc	6.4ab	11.7	15.6ab	30.6a
Agrimek+NIS	2.5	8.7	5.5abc	5.7bc	20.8	13.4b	17.9bc
Admire Pro	2	4.6	4.7bcd	4.8bc	7.6	14.7ab	15.0cb
Endigo	5	10.8	4.2cd	3.1cd	26.3	5.8bc	5.7cd
Water*	100g/a	10.1	3.9cd	4.8cb	17.8	10.7bc	19.7ab
Voliam Express	9	10.2	3.2cd	3.4cd	21.6	6.3bc	9.7bcd
Fulfill+NIS	4	8.7	2.7cd	4.7cb	9.8	2.5c	12.3bcd
Beleaf	2.8	8.4	2.4d	1.0d	21.3	2.2c	1.9d
LSD (P=0.05)		6.0	3.2	2.9	15.8	10.6	12.5
P>F		NS	0.0039	<0.0001	NS	0.0017	<0.0001

The Entomology Science Conference 2010

The Entomology Science Conference 2010 (Texas A&M - College Station) was highly informative. It included entomological research summaries and discussions on cotton, pecan, corn, soybean, potato, sorghum, rice, grape, turfgrass, insecticide resistance, insect physiology, urban pests, ornamental plants, livestock, and others. Following, I present highlights of some of the presentations on cotton and pecan at this meeting:

      Cotton Entomology Research in the High Plains: Overview and Potential Areas of Collaboration / Megha Parajulee and David L. Kerns: The Texas High Plains is the engine of the U.S. cotton industry. This is the world’s most concentrated cotton-producing region. Research areas include insect-plant interaction, molecular ecology, biology & behavior, systematics & morphometry. A multi-year area-wide survey identified alfalfa, sunflowers, mustard, pigweed, and Russian thistle as primary hosts of Lygus hesperus.  Russian thistle and alfalfa are the hosts that consistently attract more adults and nymphs. Cotton has a tremendous ability to compensate fruit loss especially if it happens during early plant stages. Up to 33% early fruit loss usually results in no significant yield differences.

      Omnivory of Western Flower Thrips (WFT) in Cotton: Implications for Management Strategies / Justin Fiene, Christian Nansen, Marvin Harris: WFT spread from western U.S. since the late 70s. Currently, they are worldwide and extremely polyphagous. WFT feeds on pollen, leaf foliage, spider mites, and mite eggs. In 2009, thrips was considered the number one pest in U.S. cotton. The cotton plant is vulnerable to thrips damage from seedling to 5-6 leaf stage, as it delays plant maturity. Female thrips feed more on plant juices than on mites. Immature thrips feed equally on plants and mites. Females live much longer than immatures and females are 35.4 times more destructive than immature thrips. Potential for host plant resistance breeding programs: in no-choice conditions, pima cotton is more susceptible than upland cotton, but in choice experiments, WFT prefer upland over pima cotton.

      Evaluation of Systemic Granular and Cotton Seed Treatment Insecticides With and Without Foliar Acephate / Roy Parker: Foliar applications of Orthene (acephate) resulted in the lowest number of thrips, but there was no effect on plant damage. Orthene applications did not result in any yield gain. Orthene had the lowest yield. Temik, Gaucho Grande, and Cruiser as seed treatmens for thrips resulted in a significant increase in cotton lint production compared to the untreated check. Temik was the highest yielding treatment.

      Effects of Neonicotinoid Insecticides on Induced Defenses to Spider Mites in Cotton and Corn / Adrianna Szczepaniec, David Kerns, Micky Eubanks: Neonicotinoids leave a good first impression: reduced environmental impact, long residual toxicity, and highly effective. However, imidacloprid has resulted in spider mite outbreaks. Why? The natural enemy elimination hypothesis has not proved conclusive, but there is increasing evidence of plant-mediated effects. Changes in plant physiology and compromised plant defense following imidacloprid applications may have a direct effect on spider mite fecundity. Imidacloprid decreased expression of defense genes in tomato plants. Thiamethoxam applications decreased expression of defense genes in cotton as well. Imidacloprid had a two-fold increment in mite abundance in tomato. However, there is no evidence of spider mite outbreaks in cotton fields following imidacloprid applications. 

      Treatment Timing Targeting Cotton Fleahoppers. When and how many treatments are needed? / Roy Parker:  This study used PHY367WRF as the cotton variety and Centric 40WG at 1.25 oz/acre to control thrips. Treatments A: 1, 2,3, 4 (weeks of squaring); B: 2, 3, 4; C: 3, 4; D: untreated check (UTC).  UTC had greater number of unopened bolls. All insecticide-treated plots had greater yields than UTC.

      Sampling Sucking Bugs and Symptoms of Boll Injury on Cotton: Are There In-season Predictors of Lint Loss, Seed Loss and Boll Rot? / Mike Brewer, Darwin Anderson, Scott Armstrong: The cotton fleahopper was the key sucking pest from squaring to bloom. Green plant bug was an important pest in late bloom. Up to 25% of bolls showed boll rot in coastal areas. Green bolls had signs of rot when infested with green plant bugs.

      Sampling Strategies for Cotton Fleahopper and the Green Plant Bug (Creontiades signatus) / Darwin Anderson, Mike Brewer, Scott Armstrong, Raul Villanueva: Treatments: visual, KISS (an air blower coupled with a sweep net), beat cloth, beat bucket, and sweep net. The beat bucket has greater advantages because it picks up less trash and it is easier to check captured insects. The sweep net has a lot of variability because insect scouts use different plant canopy depth, force, and net impact angle. KISS takes the shortest time, picks up very little trash, and is very efficient in sampling young plants. Experience plays a large role in sampling accuracy especially as plants become larger.  The beat bucket and sweep net performed better especially for experienced samplers.

      Evaluation of New Insecticides for Cotton Aphid Control / Brant Baugh, David Kerns, Rick Minzenmayer, Dustin Patman, Chris Sansone: CMT-4586 at 8 fl oz/A (spirotetramat + imidacloprid) performed well. Intruder at 0.6 oz (acetamiprid); Centric 2.5 oz (thaimethoxam); Bidrin 8 fl oz (dicrotophos); Trimax Pro 1.8 oz (imidacloprid); Carbine 1.5 oz. (flonicamid); Belay 4 oz (clothianidin)=was a poor performer. Neonicotinoids are hard on lady beetles. Carbine is easy on beneficials. Intruder, Bidrin, and carbine are good choices for aphid control.

      Controlling Mixed Populations of Bollworms, Fall Armyworms and Pink Bollworm Monitoring / Manda Cattaneo, Brant Baugh, Dustin Patman, Warren Multer, Tommy Doederlein, Charles Allen, David Kerns: Applications of Mustang Max, Karate, or Holster resulted in good bollworm control. Belt performed poorly.

            Imidacloprid Resistance Monitoring and Insecticide Efficacy Screening in Pecans / Bill Ree: Black-margined aphids: in laboratory studies, concentrations of imidacloprid at ¼ of the lowest recommended rate (according to the label) in aphid samples obtained from an organic orchard (no insecticide used in the last 12 years) resulted in 100% mortality of black-margined aphids one day after treatment. Using aphid samples obtained from a "problem orchard", 16% of black-margined aphids survived, at the highest labeled rate (7 oz/A), after 3 days of exposure. This shows a wide range of susceptibility. Stink bug tests: bifenthrin applications (Brigade WSB) at 8 and 12 oz/A provided 93 and 100% mortality at 7 days with 48 hour exposure respectively. Brigadier (bifenthrin + imidacloprid) provided good control at the lowest and highest labeled rates, resulting in 90 and 87% mortality at 7 days, with 48 hr exposure, respectively